Participation of cat motor cortex neurons in the afferent reorganization of the "placing reaction"

Neuronal activity of the cortical representation of the biceps (CRB) and triceps in the cat pericruciate motor cortex and EMG of the forepaw muscles were recorded during the performance of unconditioned (to a stimulation of the dorsal side of the paw) and conditioned (to ventral stimulation) placing reactions of the forepaw (PR). After learning: 1) ventral stimulation acquired the capacity to evoke (with a latency not exceeding 20 ms) the same enhancement of the CRB neuronal activity, as evoked by dorsal stimulation eliciting PR in naive animals; 2) EMG thresholds of biceps response to stimulation of the motor cortex through a microelectrode did not change: 3) likewise unchanged was the relative number and magnitude of CRB neuronal responses to a local tactile stimulation of the ventral side of the contralateral forepaw. The constanct sensory input to the motor cortex after learning apparently acquires the capacity to evoke an enhancement of CRB neuronal activity sufficient for achieving PR.